<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 伪类:https://developer.mozilla.org/zh-CN/docs/Web/CSS/Pseudo-classes */
    /* 需求:鼠标放上去,文字颜色变为红色 */
    /* :hover 伪类 */
    div:hover {
      color: rgb(255, 0, 0);
    }
  </style>
</head>

<body>
  <div class="box">我是div1元素</div>
  <div class="box">我是div2元素</div>
  <div class="box">我是div3元素</div>

  <a href="http://github.com">github</a>
</body>

</html>